KR20020074232A - X-ray projection exposure device, x-ray projection exposure method, and semiconductor device - Google Patents

Abstract

Provided is an X-ray projection exposure apparatus capable of exposing a desired fine pattern to a circuit pattern on a wafer with high accuracy. This X-ray projection exposure apparatus includes an X-ray source, an X-ray illumination optical system for irradiating an X-ray generated from the X-ray source onto a mask having a predetermined pattern, a mask stage for supporting the mask, and a mask from An X-ray projection optical system 1 for receiving an X-ray and projecting an image of this pattern onto a resist-coated wafer, a wafer stage 5 for supporting the wafer 4, and a mark 4a formed on the wafer 4 Is provided with a mark position detector port 6 for detecting the position. In addition, the center 36 of the exposure field of the X-ray projection optical system 1 is at a position away from the central axis 1a of the optical system 1. In addition, the center axis 6a of the mark position detector sphere 6 is on the exposure field side with respect to the center axis 1a of the X-ray projection optical system 1.

Description

X-ray projection exposure apparatus, X-ray projection exposure method and semiconductor device {X-RAY PROJECTION EXPOSURE DEVICE, X-RAY PROJECTION EXPOSURE METHOD, AND SEMICONDUCTOR DEVICE}

Technical Field

The present invention relates to an X-ray projection exposure apparatus for transferring a circuit pattern on a photomask (mask or reticle) onto a substrate such as a wafer through a reflective imaging optical system using X-rays having a wavelength of 1 to 30 nm. Moreover, it is related with the exposure method using this X-ray projection exposure apparatus, and the semiconductor device produced with this X-ray projection exposure apparatus.

Background

Background Art [0002] An exposure apparatus for manufacturing a semiconductor currently used industrially is to project-transfer a circuit pattern formed on a surface of a photomask (hereinafter referred to as a mask) as an object surface onto a substrate such as a wafer through a projection optical system. The imaging elements (lens and the like) of the mask and the projection optical system are both transmission systems. Examples of the exposure light source include i-rays of a high pressure mercury lamp, a KrF laser light source, and the like.

5 is a conceptual diagram of an exposure apparatus of a light transmission system.

This exposure apparatus includes a light source (not shown), an illumination optical system 50, a projection optical system 51, a mask stage 53 for supporting the mask 52, and a wafer stage 55 for supporting the wafer 54. ), A wafer mark position detector mechanism 56, a mask mark position detector mechanism (not shown), and the like.

In addition, a wafer surface position detector or the like is also provided. The instrument irradiates the light beam obliquely on the wafer, for example, and detects the reflected light flux with a photodetector. By this mechanism, the surface position in the optical axis direction of the wafer can be known. Specific examples of such a surface position detection mechanism are disclosed in Japanese Patent Laid-Open Nos. 6-283403, 8-64506, and Japanese Patent Laid-Open No. 10-214783.

The mark position detector tool detects the mark positions formed on the wafer and the mask by optical means.

The mask 52 is formed with an equal magnification or enlargement pattern of the pattern to be transferred to the wafer 54.

The projection optical system 51 is usually composed of a plurality of lenses or the like to form a pattern on the mask 52 on the wafer 54 so as to collectively transfer the light, and has an exposure field of about 20 mm. Therefore, the desired area (for example, the area for two semiconductor chips) can be collectively exposed.

Since the circuit of a semiconductor device is formed in multiple layers, when producing a semiconductor device by the lithographic method using a projection exposure apparatus, high-precision overlap exposure is performed on the circuit already formed on the wafer. In order to secure the overlapping accuracy, a mechanism for precisely detecting the positions of the mask 52 and the wafer 54 during exposure is required. As such a mechanism, an interferometer (not shown) for measuring the position of the mask stage 53 or the wafer stage 55 in real time, and the wafer 54 and mask used for obtaining reference positions of the two stages ( A mark position detector mechanism 56 (not shown in the mask detection mechanism on the mask side) that detects a mark (not shown) formed on 52 is used as an optical means.

The mark position detector mechanism 56 has a configuration such as an optical microscope, for example, and detects an enlarged image of the mark with an image detector such as a CCD. The mark position detector sphere is often disposed adjacent to the projection optical system 51 due to the constraints on the arrangement of the devices. A specific example of such a mark position detector tool is disclosed in Japanese Patent Laid-Open No. 5-21314.

6 is an explanatory diagram showing a relationship between an exposure field on an exposure surface and a detection center of a mark position detector port.

The hatched area in the center of FIG. 6 is the exposure field 62, and the center thereof is the exposure field center 61. As shown in FIG. In this example, the exposure field 62 is rectangular. The straight line of the dashed-dotted line extending horizontally in the figure which passed through the exposure field center 61 and parallel to the drive shaft of the wafer stage is the x-direction center line 64. A center line 65 in the y direction crosses the center line 64 at right angles at the exposure field center 61.

In the conventional general exposure apparatus, the central axis of the projection optical system coincides with the center point 61 of the square or rectangular exposure field 62. This is because the lens of the projection optical system of the transmission refraction system has an axisymmetric shape, and the optical aberration of the center part is small, so it can be said that it is a principle to use the field of vision near this axis.

Next, the detection center 63 will be described. When the optical detection mechanism is used as the mark position detector mechanism 56 (see FIG. 5), the detection center 63 is the center point 61 of the exposure field so that the mark position detector mechanism 56 and the projection optical system 51 do not interfere. It is arranged at a position away from the predetermined distance (BL in the drawing). The detection center 63 is substantially an intersection of the central axis of the optical system of the mark position detector mechanism 56 and the wafer surface. The distance BL is approximately equal to the dimension obtained by adding the radius of the barrel of the projection optical system 51 and the radius of the optical barrel of the mark position detector port 56. If the direction coinciding with the drive axis of the wafer stage is the x-direction center line 64 shown in FIG. 6 and the direction perpendicular to this is the y-direction center line 65, the projection is performed on these lines (x-axis or y-axis). In many cases, it arrange | positioned in any one of four points of the positions 63a, 63b, 63c, and 63d in BL distance from the optical system center point 61. FIG.

At the time of exposure, the distance BL of the center of the exposure field 61 and the detection center 63 of the mark position detector sphere is measured in advance. Then, the mark position on the wafer is detected by the mark position detector, and the coordinates of the position on the wafer to be exposed are obtained from the relationship between the previously known mark position and the position on the wafer to be exposed and the baseline. The wafer stage is moved to coincide with the central position of the field of view.

By the above method, the exposure field was positioned at a desired position on the wafer, and the pattern could be transferred to the position.

However, in recent years, integration of semiconductor circuits and high performance have been further progressed, and it has been required to further improve the resolution of an exposure apparatus. In general, the resolution W of the exposure apparatus is mainly determined by the exposure wavelength λ and the numerical aperture NA of the imaging optical system, and is expressed by the following equation.

W = K1 λ / NA k1: Integer

Therefore, in order to improve the resolution, it is necessary to shorten the wavelength of exposure light or to increase the numerical aperture. As described above, i-rays having a wavelength of 365 nm are mainly used for the exposure light source of the exposure apparatus currently used in the manufacture of semiconductors, and a resolution of about 0.5 to 0.5 µm is obtained. Since it is difficult for the optical design to increase the numerical aperture beyond this, shortening the wavelength of the exposure light is pursued.

Therefore, for example, an excimer laser is used as exposure light of shorter wavelength than i line | wire recently. Since the wavelength is, for example, 248 nm in KrF and 193 nm in ArF, resolution of 0.25 mu m in KrF and 0.18 mu m in ArF is obtained.

When X-rays with shorter wavelengths are further used as exposure light, for example, when the wavelength is 13 nm, a resolution of 0.1 µm or less is obtained.

In the case of such an X-ray projection exposure apparatus, since a lens material having good X-ray transmittance is not industrially obtained, it is necessary to configure all of the projection imaging optical systems with reflecting mirrors. In the case of the reflective optical system, it is difficult to design an optical system with a wide field of view near the central axis of the optical system. On the other hand, if the exposure field of the projection optical system is formed at a position away from the central axis of the optical system (so-called axial separation optical system), for example, in the shape of a ring, high resolution can be obtained within the long exposure field.

In addition, by scanning a mask and a wafer at the time of exposure, the semiconductor chip of 20 mm or more can be exposed by the imaging optical system of a small field of view. According to the X-ray projection exposure apparatus using such a method, a desired exposure area can be secured.

7 is a conceptual diagram of an X-ray projection exposure apparatus currently being devised.

The main components of the X-ray projection exposure apparatus mainly include the X-ray light source 77, the X-ray illumination optical system 78, the X-ray projection optical system 71, the mask 72, the mask stage 73, the wafer 74, Wafer stage 75.

The X-ray light source 77 is, for example, a discharge plasma X-ray light source. The illumination optical system 78 consists of several stages of reflection lenses, a filter, etc., and irradiates a ring-shaped illumination light toward the mask 72.

The X-ray projection optical system 71 is composed of a plurality of reflecting mirrors and the like, and forms a pattern on the mask 72 on the wafer 74. On the surface of each reflecting mirror, a multilayer film for enhancing the reflectance of X-rays is formed. The X-ray projection optical system 71 has a ring-shaped exposure field and transfers a portion of the ring-shaped region pattern of the mask 72 to the surface of the wafer 74.

The mask 72 is a reflection type, and a circuit pattern is formed in the reflection surface. Since the mask is a reflective type, the X-ray projection optical system 71 is an optical system in which the mask side is non-telecentric.

Since X-rays having a wavelength of 1 to 30 nm have a large absorption by air, at least the X-ray optical path of the X-ray exposure apparatus is preferably maintained in a reduced pressure atmosphere, a He atmosphere, or a vacuum environment. Most preferably, it is set as a vacuum environment. For this reason, the optical system of the X-ray projection exposure apparatus is arranged in a vacuum chamber (not shown).

In the semiconductor device, since the circuit is formed over a plurality of layers, the following circuit pattern is overlaid on the circuit already formed on the wafer, even when transferring the pattern of the semiconductor device with the X-ray projection exposure apparatus. In order to perform this superimposition exposure with high precision, the mechanism which detects the position of the mask 72 and the wafer 74 under exposure precisely is needed. As such a mechanism, the interferometer (not shown) which measures the position of the mask stage 73 and the wafer stage 75 in real time, and the wafer 74 and the mask which are used in obtaining the reference position of the said both stages A mark position detector mechanism (not shown) for detecting a mark (not shown) formed on the 72 by optical means is used.

However, when transferring the pattern of the semiconductor device, it is necessary to project the image of the pattern to a desired position on the wafer. The positional accuracy of this image needs to be at least smaller than the minimum line width of the formed pattern, and preferably 1/4 or less of the minimum line width of the pattern is required. Therefore, as the resolution of the exposure apparatus is improved, the positional accuracy of the pattern, that is, the overlapping accuracy, must also be improved.

Since the X-ray projection exposure apparatus has a smaller minimum line width of the projection pattern than the conventional light projection exposure apparatus, it is also necessary to improve the overlapping accuracy. In order to improve the overlapping accuracy, improvement of detection accuracy of alignment marks, improvement of driving accuracy of the wafer stage, and improvement of baseline stability are required. The stability of the baseline refers to the degree to which this value is kept constant until exposure after measuring the baseline (the distance between the exposure field center and the mark position detector sphere, BL in FIG. 6). If this is unstable, the exposure position cannot be matched to the desired position of the wafer, resulting in an overlap error. The baseline fluctuates due to deformation of the projection optical system barrel, deformation of the support mechanism, and the like. Therefore, the stability of the baseline depends on the stability of the barrel, the mark position detector, and the supporting mechanism supporting them, and the length of the baseline. When the mark position is detected and the position and posture of the wafer are aligned, the wafer stage is driven from the detection position of the mark position detector to the exposure position. Therefore, when the baseline, which is the distance between the detection position of the mark position detector tool and the exposure field length, becomes long, the driving distance of the wafer stage becomes long, and the positional accuracy of the stage also decreases, resulting in poor overlapping accuracy.

The X-ray projection exposure apparatus currently proposed is difficult to secure sufficient baseline stability, and as a result, there is expected a problem that it is not possible to obtain superposition accuracy suitable for resolution. As a result, there is a fear that the yield of the semiconductor device to be manufactured cannot be guaranteed.

The present invention has been made in view of the above problems, and an object thereof is to provide an X-ray projection exposure apparatus capable of exposing a desired fine pattern to a circuit pattern on a wafer with high accuracy.

Disclosure of the Invention

The present invention relates to an X-ray source and an X-ray illumination optical system for irradiating an X-ray generated from the X-ray source onto a mask having a predetermined pattern, a mask stage for supporting the mask, An X-ray projection optical system that receives X-rays and projects an image of this pattern onto a resist-coated wafer, a wafer stage for supporting the wafer, and a mark position detection for detecting positions of the wafer or marks formed on the wafer stage. An X-ray projection exposure apparatus having a mechanism, wherein the exposure field of the X-ray projection optical system is located at a position away from the central axis of the optical system, wherein the detection center of the mark position detector sphere is located at the center axis of the X-ray projection optical system. On the other hand, the X-ray projection exposure apparatus (claim 1), which is on the side of the exposure field of view, is provided.

In addition, the present invention is a second X-ray source, an X-ray illumination optical system for irradiating an X-ray generated from the X-ray source onto a mask having a predetermined pattern, a mask stage for supporting the mask, and this mask An X-ray projection optical system that receives X-rays from the image and projects the image of this pattern onto a resist-coated wafer, a wafer stage for supporting the wafer, and a mark for detecting the position of the wafer or the mark formed on the wafer stage An X-ray projection exposure apparatus including a position detector, wherein the exposure field of the X-ray projection optical system is located at a position away from the central axis of the optical system. In the case where the xy coordinate system is determined so that the center of the exposure field is at a position where x <0 on the x axis, with the intersection of the image plane as the origin, the detection center of the mark position detector sphere. An x-ray projection exposure apparatus (claim 2) is provided in the region where x?

In addition, the present invention is the third, "the detection center is arranged on the x-axis or on a straight line orthogonal to the x-axis past the center point of the exposure field of the X-ray projection optical system, X according to claim 2 characterized in that Line projection exposure apparatus (Claim 3).

The fourth aspect of the present invention provides the X-ray according to claim 1 or 2, wherein the mark position detector sphere irradiates visible, infrared or ultraviolet light to the mark and detects the reflected light, scattered light, or diffracted light. Projection Exposure Equipment (Claim 4).

Further, the fifth aspect of the present invention is that the mark position detector is composed of an optical system, and the optical system has a function of correcting a change in focus position due to a change in refractive index of an optical path medium. Line projection exposure apparatus (Claim 5).

In addition, the present invention is the sixth, "X-ray generated from the X-ray source is irradiated on the mask having a predetermined pattern, the mask is supported on the mask stage, the image of the pattern of the mask on the wafer coated with a resist The wafer is supported on the wafer stage, the position of the wafer or the mark formed on the wafer stage is detected using a mark position detector, and the exposure field of the X-ray projection optical system is determined from the central axis of the optical system. On the image plane of the X-ray projection optical system, the xy coordinate system is defined so that the center of the exposure field is at a position where x <0 on the x axis, with the intersection of the center axis of the optical system and the image plane as the origin. In this case, the detection center of the mark position detector sphere is placed in an area of x ≦ 0, and based on the detection signal of the mark position detector sphere, Driving the buffer stage to, and provides an X-ray projection exposure method (claim 6) "as to form the projection image of the circuit pattern formed on the mask in the desired position of the wafer.

According to a seventh aspect of the present invention, the distance between the origin of the xy coordinate system and the center point of the exposure field of the X-ray projection optical system is measured, and the driving amount of the wafer stage is determined based on the value. An X-ray projection exposure method (claim 7) according to claim 6 is provided.

Moreover, this invention provides the 8th "semiconductor device (claim 8) characterized by exposing and producing by the X-ray projection exposure method of Claim 6 or 7."

Brief description of the drawings

1 is a schematic diagram of an X-ray projection exposure apparatus according to the present invention.

2 is a diagram illustrating a specific configuration example of a mark position detector mechanism.

3 is a view showing the positional relationship between the exposure field of the X-ray projection exposure apparatus and the detection center of the mark position detector according to the present invention.

4 is a schematic diagram of an X-ray projection exposure apparatus according to the present invention.

5 is a conceptual diagram of an exposure apparatus of a light transmission system.

Fig. 6 is an explanatory diagram showing the relationship between the exposure field of the conventional exposure apparatus and the detection center of the mark position detector.

7 is a conceptual diagram of an X-ray projection exposure apparatus currently being devised.

Best Mode for Carrying Out the Invention

1 is a schematic diagram of an X-ray projection exposure apparatus according to the present invention.

The main components of the X-ray projection exposure apparatus of the present invention are an X-ray circle 41, an X-ray illumination optical system 42, an X-ray projection optical system 1, a mask stage 3 for supporting a mask 2, a wafer A wafer stage 5 supporting the wafer 4, a wafer mark position detector sphere 6, and a mask mark position detector sphere (not shown).

The X-ray source 41 is, for example, a discharge plasma X-ray light source. The X-ray illumination optical system 42 consists of several stages of lenses, filters, etc., and irradiates the ring-shaped illumination light toward the mask 2. The mask 2 is of a reflective type, and an equal magnification or enlargement pattern of the pattern drawn on the wafer 4 is formed on the reflective surface. The X-ray projection optical system 1 has a ring-shaped exposure field and is composed of a plurality of reflecting mirrors and the like. Since the mask 2 is a reflection type, the optical system 1 is an optical system in which the mask side is non-telecentric. The pattern of the mask 2 is imaged on the surface of the wafer 4 in the X-ray projection optical system 1. At this time, the mask 2 and the wafer 4 are synchronously scanned at a constant speed, the pattern region of the mask 2 is selectively exposed, and transferred to the surface of the wafer 4.

In addition, since X-rays having a wavelength of 1 to 30 nm have a large absorption by air, the X-ray optical path of the X-ray exposure apparatus is preferably maintained in a reduced pressure atmosphere, a He atmosphere, or a vacuum atmosphere. Most preferably, it is a vacuum atmosphere, and the optical system of an X-ray projection exposure apparatus is arrange | positioned in the vacuum chamber (not shown).

The wafer mark position detector mechanism 6 is, for example, an apparatus for detecting the position of the mark 4a on the wafer and the mark (not shown) on the wafer stage by optical means or the like. Wafer coordinates are set based on the wafer position information obtained from this mechanism to drive the wafer stage, and the pattern on the mask is exposed to a desired position on the wafer.

2 is a diagram illustrating a specific configuration example of a mark position detector mechanism.

The wafer mark position detector mechanism 6 in this example is the same as the optical microscope. The wafer stage 5 is positioned so that the wafer mark 4a is directly under the optical axis 6a (detection center) of the mark position detector mechanism 6, and the enlarged image of the mark 4a is placed in a detector 21 such as a CCD. ), The position of the mark is detected by image processing. The wafer mark position detector mechanism 6 of this example includes a light source (not shown) that emits light that the resist hardly exposes, an illumination optical system (not shown) that irradiates the mark with light emitted from the light source, and an image of the mark on the detector. It consists of the detection optical systems 22 and 23 to enlarge and project, and the detectors 21, such as CCD. By increasing the numerical aperture of the detection optical system, a high contrast mark image can be obtained, and highly accurate mark position can be detected. The position adjusting mechanism 24 is provided in the mark position detector mechanism 6, which will be described later.

Next, with reference to FIG. 3, the positional relationship of the exposure field and the detection center of a wafer mark position detector tool in the X-ray projection exposure apparatus of this invention is demonstrated.

This figure shows the case where the exposure field 31 has a ring-shaped shape, which is a view of the plane (image plane of the X-ray projection optical system) including the exposure field 31 as viewed from above. In this example, the exposure field 31 is an area sandwiched between two circular arcs 33 and 34 having a predetermined radius and an opening angle around the center axis of the X-ray projection optical system and the intersection 32 of this image plane. In the above-described reflective optical system, it is difficult to set a wide field of view in the vicinity of the central axis of the optical system, and thus the exposure field of such an arc shape (ring-shaped) is obtained.

The detection center of the wafer mark position detector sphere 6 is the center of the X-ray projection optical system 1 due to the limitation of mechanical interference between the mark position detector sphere 6 and the X-ray projection optical system 1 as shown in FIG. 2. It is arrange | positioned at the place which is a fixed distance from axis 1a. Usually, since the mark position detector sphere 6 is mounted on the side wall of the barrel of the projection optical system 1, the center axis 6a (ie detection center) of the mark position detector sphere 6 and the center axis of the projection optical system 1 ( The distance of 1a) is a value which adds the radius R (for example, 300 mm) of the projection optical system 1 (barrel) to the radius r (for example, 50 mm) of the mark position detector port 6 (barrel).

In the present invention, as shown in Fig. 3, on the image plane, the center axis (36: center of the projection optical system) of the X-ray projection optical system and the intersection of the image plane as the origin and the center point (36) of the exposure field 31 ) When the xy coordinate system at which x <0 is located on the x-axis is determined, the detection center 35a of the wafer mark position detector sphere 6 is placed in an area where x ≤ 0 (area 39 indicated by diagonal lines in the drawing). To place.

That is, the x coordinate is set so that the line connecting the origin 32 of the projection optical system center and the center 36 of the exposure field 31 is the x-axis, and the exposure field center 36 becomes negative when viewed from the origin 32. Take Similarly, the mark detection center 35a is also placed on the negative side (including 0). In other words, it can be said that the detection center 35a of the mark position detector sphere is on the exposure field 31 side with respect to the projection optical system central axis 1a. In addition, this x-axis generally coincides with the axis | shaft which scan-transfers a wafer stage.

By arranging the detection center 35 in the region 39, the baseline BL (the distance between the detection center 35 and the exposure field sight 36) can be made smaller than in the case where the detection center 35 is arranged in another location. As a result, the driving distance of the wafer stage from the alignment position to the exposure position can be shortened, and the stability of the baseline is improved. In particular, placing the detection center at the point 35a on the x-axis improves the stability of the baseline.

In addition, even when the detection center is disposed at the points 35b and 35c on the straight line 37 (y-axis parallel line) orthogonal to the x-axis passing through the center point 36 of the exposure field, the grasp of coordinates becomes simple and the stability of the baseline is improved. do.

Also, in the hatching area 39, a mark position detector can not be placed at a position that interferes with the optical barrel of the projection optical system. Actually, the distance R + r shown in Fig. 2 from the origin 32 is shown. The radius of the detector opening). The shortest baseline BL is in the case of the detection center 35a on the x-axis of FIG. 3, and the dimension of the baseline BL in this case is the distance between the origin 32 and the exposure field center 36 at R + r. F is subtracted.

It is preferable that the mark position detector sphere irradiates visible, infrared or ultraviolet light to the mark and detects the reflected light, scattered light or diffracted light. By employing the optical detection method, high detection accuracy can be obtained. In particular, when the wavelength band of the detection light is widened, the interference effect of light inside the resist is reduced, and the detection accuracy is improved.

In addition, when the mark position detector sphere is composed of an optical device and a part of the optical system is disposed in a vacuum which is an exposure environment, it is preferable to design the difference in refractive index between the environmental medium and the optical element as the difference in refractive index between vacuum and glass. As a result, a high resolution optical system can be produced, and the mark position detection accuracy is improved.

On the other hand, when adjusting the mark position detector mechanism, the adjustment becomes easy as long as it can be adjusted in the air. At this time, the optical system designed so that the aberration is optimal in vacuum does not necessarily mean that the same aberration characteristic is obtained in the atmosphere. In particular, the focal length is often changed greatly. Therefore, it is desirable to provide a focus position correction mechanism in the mark position detector. By providing this function, the mark position can be detected even in the air, and the mark position detector can be easily adjusted.

The correction mechanism can, for example, move a part of the lens constituting the optical system in the optical axis direction. It is conceivable that the optical system of the mark position detector tool is arranged in the vacuum chamber or a part thereof in the vacuum chamber and the rest in the vacuum chamber. In the former case, since the position adjustment of the lens or the like needs to be performed in a vacuum, as shown in Fig. 2, by arranging an actuator 24 such as a motor that can be driven in the vacuum, the lens in the vacuum can be remotely operated. It is preferable because of that. In the latter case, the adjusting mechanism may be arranged in a vacuum in the same manner as the former one, but preferably it is preferably arranged outside the vacuum chamber. This makes the adjustment mechanism low cost.

The mark position detector sphere is not limited to the optical detector sphere. The mechanism may be irradiated with an electron beam, an X-ray, a particle beam, and detects the reflection, scattering, diffraction, transmission, or excitation of the electron beam, X-ray, or particle beam. Since the exposure environment is a vacuum, the X-ray projection exposure apparatus is easily absorbed by the air among the electron beams, X-rays, and particle beams, and can be detected using a conventional detection apparatus that was difficult to detect. By using such a feature, high detection accuracy can be achieved by means different from the conventional exposure apparatus.

EMBODIMENT OF THE INVENTION Hereinafter, although this invention is demonstrated further more concretely, this invention is not limited to these examples.

Fig. 4 shows an X-ray projection exposure apparatus according to the first embodiment of the present invention.

The apparatus mainly includes a mask stage 3 for supporting an X-ray light source (not shown), an X-ray illumination optical system (not shown), an X-ray projection optical system 1, and a mask 92, and a wafer stage for supporting a wafer 4. (5), wafer mark position detector sphere 6, mask mark position detector sphere (not shown), vacuum chamber 7, base member 8 for supporting barrel, and vibration damping table for supporting base member 8 ( 9) consists of.

This apparatus uses a laser plasma X-ray source as an X-ray light source, and the X-rays emitted thereon are irradiated onto the mask 2 through an X-ray illumination optical system. At this time, an exposure wavelength is 13.5 nm, for example, and the mask 2 uses a reflective type. The X-ray 11a reflected by the mask 2 passes through the X-ray projection optical system 1 to reach the wafer 4, and the mask pattern is reduced-transferred on the wafer 4.

The X-ray projection optical system 1 is composed of six reflecting mirrors, has a magnification of 1/4, and has a ring-shaped exposure field of 2 mm in width and 30 mm in length. Six reflecting mirrors are supported in the barrel. By invading the barrel, thermal deformation can be prevented from occurring easily.

The reflecting mirror has an aspherical surface with a reflecting surface, and the surface is coated with a Mo / Si multilayer film for improving the reflectance of X-rays. In detail, the Mo layer is formed by alternately stacking the Mo layer and the Ru layer, and uses an internal stress of 30 MPa or less in the multilayer film.

At the time of exposure, the mask 2 and the wafer 4 are scanned by the mask stage 3 and the wafer stage 5, respectively. The scanning speed of the wafer is always synchronized so that it is 1/4 of the scanning speed of the mask. As a result, the pattern on the mask can be reduced to 1/4 on the wafer and transferred.

The wafer mark position detector mechanism 6 can use the above-mentioned special optical microscope. An enlarged image of a mark on the wafer is picked up by a CCD and the position of the wafer is detected by image processing.

The detection center of the wafer mark position detector mechanism 6 is arranged at the position of the point 35a on the x-axis as shown in FIG. That is, the wafer mark position detector mechanism is arranged so that the image of the mark at this position can be observed. At this time, the wafer mark position detector sphere 6 is disposed so that the baseline (BL in FIG. 3), which is the distance between the center point 36 of the exposure field and the detection center 35a, is made as small as possible.

The wafer mark position detector mechanism 6 is fixed to the base member 8. The base member 8 is disposed on the vibration damping table 9 so that vibration is not easily transmitted to the X-ray projection optical system and the wafer mark position detector. The shock absorbing member 10 such as a bellows is sandwiched between the vacuum chamber 7 and the base member 8 so that vibrations from the mask stage 3, the wafer stage 5 and the like are not transmitted to the base member. have. With the above configuration, the positional relationship between the X-ray projection optical system 1 and the wafer mark position detector sphere 6 is kept substantially constant.

By the above mechanism, the position of the mark of the wafer can also be detected with high accuracy of 10 nm or less. In addition, the baseline can also obtain stability of 10 nm or less. The exposure apparatus according to the present invention exposes the exposure pattern with high accuracy by overlapping the circuit pattern formed on the wafer surface on the basis of the detection result, and exposes a resist pattern with a minimum size of 0.07 μm for one semiconductor chip on the wafer as a desired region. The whole surface can be obtained in a desired shape. The device can also be manufactured with high throughput and high throughput.

An example of exposing to a wafer coated with a resist using the X-ray projection exposure apparatus of the above-described embodiment will be described.

In the case of exposure, the several mark on the wafer surface is previously detected by a mark position detector port, and the space | interval of a mark is measured. And the magnification correction amount optimal for exposure is computed from the difference of a measured value and a design value. Then, the mask and the wafer are respectively moved in the optical axis direction of the X-ray projection optical system to correct the projection magnification.

Next, the baseline, which is the distance between the exposure field center and the detection center, is measured.

Further, the marks on the wafer surface and the mask surface are detected by the wafer mark position detector sphere and the mask mark position detector sphere. Based on the measured baseline values, the wafer stage and the mask stage are driven to adjust the wafer position so that the projection pattern is formed below a desired superposition accuracy on the circuit pattern already formed on the wafer surface.

By the above exposure method, a resist pattern having a minimum size of 0.07 占 퐉 can be obtained in a desired shape on the entire surface of the region for one semiconductor chip on the wafer as the desired region. The superposition accuracy at this time can expect 10 nm or less.

The method of manufacturing a semiconductor device by the exposure method of the above-mentioned example using the above-mentioned X-ray projection exposure apparatus is demonstrated.

The device is, for example, 16 GB (gigabyte) of DRAM. This device has 22 layers of circuits, and 15 of them are exposed by the X-ray projection exposure apparatus according to the present invention. Since the remaining seven layers have a minimum pattern size of 0.15 mu m or more, they are exposed by an excimer laser exposure apparatus. A device circuit is fabricated by performing resist coating, doping, annealing, etching, deposition, and the like between the exposures. Finally, the silicon wafer is cut and divided into chip shapes, and each chip is packaged in a ceramic package.

The semiconductor device manufactured as described above can have a large capacity of 16 GB and exhibit desired electrical characteristics.

Industrial availability

As described above, according to the X-ray projection exposure apparatus of the present invention, the baseline can be stably maintained. As a result, even a process wafer with a large amount of deformation can be exposed at high throughput with high overlapping accuracy.

Claims (8)

X-ray circle; An X-ray illumination optical system for irradiating an X-ray generated from the X-ray source onto a mask having a predetermined pattern; A mask stage for supporting the mask; An X-ray projection optical system for receiving X-rays from the mask and projecting the image of the pattern onto a wafer coated with a resist; A wafer stage for supporting the wafer; And A mark position detector for detecting a position of a mark formed on the wafer or the wafer stage, An X-ray projection exposure apparatus in which an exposure field of the X-ray projection optical system is located away from a central axis of the optical system, And the detection center of the mark position detector is on the side of the exposure field with respect to the central axis of the X-ray projection optical system. X-ray circle; An X-ray illumination optical system for irradiating an X-ray generated from the X-ray source onto a mask having a predetermined pattern; A mask stage for supporting the mask; An X-ray projection optical system for receiving X-rays from the mask and projecting the image of the pattern onto a wafer coated with a resist; A wafer stage for supporting the wafer; And A mark position detector for detecting a position of a mark formed on the wafer or the wafer stage, An X-ray projection exposure apparatus in which an exposure field of the X-ray projection optical system is located away from a central axis of the optical system, On the image plane of the X-ray projection optical system, when the xy coordinate system is determined so that the center of the exposure field is at a position where x <0 on the x axis, with the intersection of the center axis of the optical system and the image plane as the origin, the mark An x-ray projection exposure apparatus, characterized in that the detection center of the position detector is in a region where x ≤ 0. The method of claim 2, And the detection center is arranged on the x-axis or on a straight line perpendicular to the x-axis past the center point of the exposure field of the X-ray projection optical system. The method according to claim 1 or 2, And the mark position detector sphere irradiates visible, infrared or ultraviolet light to the mark and detects the reflected light, scattered light or diffracted light. The method according to claim 1 or 2, And said mark position detector sphere comprises an optical system, said optical system having a function of correcting a change in focus position due to a change in refractive index of a medium of an optical path. X-rays generated from X-ray circles are irradiated onto a mask having a predetermined pattern, Support the mask to a mask stage, Project an image of the pattern of the mask onto a wafer coated with a resist, Supporting the wafer on a wafer stage, The position of the mark formed on the wafer or the wafer stage is detected using a mark position detector; The exposure field of the X-ray projection optical system is located at a position away from the central axis of the optical system, On the image plane of the X-ray projection optical system, when the xy coordinate system is determined so that the center of the exposure field is at a position where x <0 on the x axis, with the intersection of the center axis of the optical system and the image plane as the origin, the mark Place the detection center of the position detector sphere in the region of x ≤ 0, And the wafer stage is driven based on the detection signal of the mark position detector to form a projected image of a circuit pattern formed in the mask at a desired position of the wafer. The method of claim 6, And measuring the distance between the origin of the xy coordinate system and the center point of the exposure field of the X-ray projection optical system, and determining the driving amount of the wafer stage based on the value. The semiconductor device was produced by exposing by the X-ray projection exposure method of Claim 6 or 7.